This study examined the effect of spinal nerve ligation on different populations of immunohistochemically identified neurons in the dorsal root ganglia (DRG) of the rat. The optical fractionator method was used to count neurons in the ipsilateral L4 and L5 DRG 1-20 weeks after ligation of the L5 and L6 spinal nerves, sham surgery, or no surgery. One week after ligation, neurons in the L5 DRG that were labeled by IB4, a marker of unmyelinated primary afferent neurons, were largely absent. The numbers of IB4-labeled neurons then progressively increased to reach control values by 20 weeks. A smaller, sustained decrease occurred in the number of small-, medium- and large-sized neurons immunoreactive for calcitonin gene-related peptide (CGRP), a marker for peptidergic primary afferents, in the L5 DRG. There was a proportionately greater decrease in the numbers of medium- to large-sized CGRP-like immunoreactive neurons. The number of myelinated afferents in the L5 DRG, identified by their staining for neurofilament protein (N52), did not change after ligation. However, closer examination revealed a significant decrease in the numbers of large-sized neurons, coupled with an increase in the numbers of small- to medium-sized neurons, and the appearance of a novel population of very small-sized neurons labeled by N52. The numbers and cell size distributions of IB4-labeled, CGRP-like immunoreactive, and N52-labeled neurons were unchanged in the adjacent L4 DRG. Unlike the L5 DRG, injury-induced changes in the expression of various receptors, neurotransmitters and neurotrophic factors in the L4 DRG are not confounded by a change in the immunohistochemical phenotype of primary afferent neurons.

Background and purposeFunctional magnetic resonance imaging (fMRI) is a non-invasive pre-surgical tool used to assess localization and lateralization of language function in brain tumor and vascular lesion patients in order to guide neurosurgeons as they devise a surgical approach to treat these lesions. We investigated the effect of varying the statistical thresholds as well as the type of language tasks on functional activation patterns and language lateralization. We hypothesized that language lateralization indices (LIs) would be threshold- and task-dependent.Materials and methodsImaging data were collected from brain tumor patients (n = 67, average age 48 years) and vascular lesion patients (n = 25, average age 43 years) who received pre-operative fMRI scanning. Both patient groups performed expressive (antonym and/or letter-word generation) and receptive (tumor patients performed text-reading; vascular lesion patients performed text-listening) language tasks. A control group (n = 25, average age 45 years) performed the letter-word generation task.ResultsBrain tumor patients showed left-lateralization during the antonym-word generation and text-reading tasks at high threshold values and bilateral activation during the letter-word generation task, irrespective of the threshold values. Vascular lesion patients showed left-lateralization during the antonym and letter-word generation, and text-listening tasks at high threshold values.ConclusionOur results suggest that the type of task and the applied statistical threshold influence LI and that the threshold effects on LI may be task-specific. Thus identifying critical functional regions and computing LIs should be conducted on an individual subject basis, using a continuum of threshold values with different tasks to provide the most accurate information for surgical planning to minimize post-operative language deficits.

Background: Functional Magnetic Resonance Imaging (fMRI) is a presurgical planning technique used to localize functional cortex so as to maximize resection of diseased tissue and avoid viable tissue. In this retrospective study, we examined differences in morbidity and mortality of brain tumor patients who received preoperative fMRI in comparison to those who did not. Methods: Brain tumor patients (n=206) were selected from a retrospective review of neurosurgical case logs from 2001–2009 at the University of Wisconsin-Madison. Results: Univariate analysis showed improved mortality in the fMRI group and the fMRI+Electrical Cortical Stimulation Mapping (ECM) group compared to the No-fMRI group. Multivariate analyses showed improved mortality of the fMRI group and the fMRI+ECM group compared to the No-fMRI group, with age and tumor grade being the most significant influencers. Overall, the fMRI group showed survival benefits at 3 years; twice that of the No-fMRI group. Furthermore, patients with high-grade tumors showed significant survival benefits in the fMRI group, while patients with low-grade tumors did not (controlling for age and ECM). There was also a significant difference in the two groups with respect to morbidity, with patients receiving fMRI showing improved outcomes in the motor and language domains. Conclusions: This study analyzing a large retrospective series of brain tumor patients with and without the use of fMRI in the preoperative planning has resulted in improved mortality and morbidity outcomes with the use of fMRI. These results point to the importance of incorporating fMRI in presurgical planning in the clinical management of patients with brain tumors.

Object Functional MRI (fMRI) is commonly used by neurosurgeons preoperatively to identify brain regions associated with essential behaviors, such as language and motor abilities. In this study the authors investigated the relationship between patient morbidity and mortality and the distance from the tumor border area to functional activations in secondary motor and language cortices. Methods Patients with primary or metastatic brain tumors who underwent preoperative fMRI motor and language mapping were selected from a large database of patients with tumors. The lesion-to-activation distance (LAD) was measured in each patient relative to the supplementary motor area (SMA) for motor tasks and the presupplementary motor area (pSMA) for language tasks. The association between LAD and the incidence of deficits was investigated using the Fisher exact tests of significance. The impact of other variables, including age, handedness, sex, and tumor grade, was also investigated. In a subset of patients, logistic regression was performed to identify the likelihood of deficits based on the LAD to primary and secondary regions. Finally, Mantel-Cox log-rank tests were performed to determine whether survival time was significantly related to the LAD to secondary motor and language areas. Results A significant association was observed between the LAD to the SMA and the incidence of motor deficits, with the percentage of patients with deficits dropping for those in the LAD > 2 cm group. The relationship between the LAD to the pSMA and the incidence of language deficits was not significant. Logistic regression demonstrated that the LAD to primary sensorimotor cortex does affect the incidence of motor deficits, but that the LAD to SMA does not. Finally, the authors observed no relationship between the LAD to secondary regions and patient mortality rates. Conclusions These results demonstrate that the LAD to SMA structures does affect morbidity, although not to the extent of LAD to primary structures. In addition, motor deficits are significantly associated with LAD to secondary structures, but language deficits are not. This should be considered by neurosurgeons for patient consultation and preoperative planning.

Measuring tumor proximity to major white matter tracts using DTI can inform clinicians of the likelihood of postoperative functional deficits. A distance of 1 cm or less from eloquent white matter structures most significantly predicts the occurrence of new deficits with current surgical and imaging techniques.